- A theory of continental growth by the addition of successive geosynclines to the craton.
- A mass of rock that has been moved a long distance from its place of origin, commonly by
a tectonic process such as overthrusting.
- Said of the rocks of the Archeozoic.
- The earlier part of two great divisions of the Precambrian
- A body of rocks that remains at its site of origin, where it is rooted to its basement.
Rocks of an autochthon may be mildly to considerably deformed.
- A part of the earth's crust that has attained stability and has been little deformed for
a long time. The term is restricted to continents.
- A diagram showing the features transected by a vertical plane, e.g. a vertical section
through an orebody, an anticline, or a fossil.
- A groupe of plutonic rocks intermediate in composition between
acidic and basic, characteristically composed of hornblende, oligoclase, or andesine,
pyroxene, and sometimes a little quartz.
- The mass of rock beneath a fault.
- Said of a rock that is able to sustain, unde a given set of condition, 5-10% deformation
before fracturing or faulting.
- A stable area marginal to an orogenic belt, toward which the rocks of the belt were
thrust or overfolded. Generally the foreland is a continental part of the crust, and is
the edge of the craton or platform area.
- Study of time in relationship to the history of the Earth, esp. by the absolute age
determination and relative dating systems developed for this purpose.
- A seismic detector, placed on or in the ground, that responds to
ground motion at its point of location.
- Broadly applied,any quartz-bearing plutonic rock composed
entirely of crystals, i.e. having no glassy part.
- A field term for any compact dark-green altered or metamorphosed basic igneous rock that
owes its color to chlorite, actinolite, or epidote.
- Grenville orogen
- A name that is widely used for a major plutonic, metamorphic, and deformational event
during the Precambrian which affected a broad province along the southeastern border of
the Canadian Shield.
- Grenville province
- A series of the Precambrian of Canada and New York.
- Overlapping, as shingles or tiles on a roof.
- An isolated rock unit that is an erosional remnant or outlier nof a nappe.
- A Canadian national Earth science research project to investigate the 3-dimensional
structural evolution of Canada's landmass and continental margins. Research is conducted
in a coordinated, integrated, multidisciplinary fashion, with seismic techniques
spearheading the research. The
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- A layer of strength relative to the underlying asthenosphere. It includes the crust and
part of the upper mantle and is of the order of 100 km in thickness.
- Said of an igneous rock composed chiefly of one or more ferromagnesian, dark-colored
minerals in its mode; also said of those minerals.
- The mineralogical, chemical, and structural adjustment of solid rocks to physical and
chemical conditions imposed at depth below the surface zones of weathering and
cementation, whcih differs from the conditions under which the rocks originated.
- metamorphic grade
- The intensity of metamorphism, measured by the degree of
difference between the parent rock and the metamorphic rock.
- Any solid object from interplanetary space that has fallen to the earth's surface
without being vaporized during its passage through the atmosphere.
- Mohorovicic discontinuity
- The boundary surface or sharp seismic-velocity discontinuity that separates the Earth's
crust from the subjacent mantle. It marks the level in the Earth at which the P-wave
velocities change abruptly from 6.7-7.2 km/sec to 7.6-8.6 km/sec on average.
- Said of a rock unit that is intermediate in tectonic character
between autochthon and allocthon.
- Said of a rock unit that is intermediate in tectonic character between autochthonous and
- Pertaining to rocks formed by any process at great depth.
- orogenic belt
- A linear or arcuate region that has been subjected to folding and other deformation
during an orogenic cycle. Orogenic belts are mobile belts during their formative stages,
and most of them later became mountain belts by postorogenic processes.
- plate tectonics
- A theory in which the surface of the Earth is made up of a number of rigid plates moving
relative to each other, separating at mid-oceanic ridges where new ocean-floor is produced
and converging at subduction zones, where one plate descends beneath another,
- The more recent of two great divisions of the Precambrian.
- All geologic time, and its corresponding rocks, before the beginning of the Paleozoic;
it is equivalent to about 90% of geologic time.
- radiometric dating
- Calculating an age in years for geologic materials by measuring the presence of a
radioactive element; based on nuclear decay of naturally occurring radioactive isotopes.
- Pertaining to an earth vibration, including those that are artificially induced.
- seismic record
- In geophysical exploration, a photographic or magnetic record of reflected or refracted
- shear zone
- A tabular zone of rock that as been crushed and brecciated by many parallel fractures
due to shear strain. Such an area is often mineralized by ore-forming solutions.
- A branch of geology dealing with the broad architecture of the outer part of the earth,
that is, the major structural or deformational features and their relations, origin, and
historical evolution. It is closely related to structural geology, but tectonics generally
deals with larger features.
- A group of plutonic rocks having the composition of diorite but
with an appreciable amount of quartz, i.e. between 5 and 20 percent.
- A thrust fault in which the footwall was the active element.
Questions or comments? (Litho@stoner.eps.mcgill.ca)